Apparatus for producing constant current



Aug. 12, 1941. J RQUGVIE 2,252,645

APPARATUS FOR PRODUCING CONSTANT CURRENT Filed May is, 1959 INVENTOR IBowyve BY ATTORNEY tube devices employed cult. The load circuit may,

a the invention given Patented'Aug. 12, 1941 James Ferguson Bougvie,Belmont, Mass., as.-

slgnor C mp a to American Telephone and Telegraph corporation of NewYork Application May 3, 1939, Serial No. 271,580

This invention relates to gas discharge tube devices and to circuitstherefor. More particularly, this invention relates to gas dischargetubes which are positioned within magnetic fields, as well as tocircuits utilizing the features of such devices. Still moreparticularly, this invention relates to magnetically controlled gasdischarge for the production of substantially constant currents.

In my copending application, Serial No. 271,579, filed of even date,there is shown and described one form of gas discharge tube device whichis arranged for the production of rectified current of substantiallyconstant amplitude to be supplied to a load circuit attached thereto.The control of the rectified current is obtained-by applying to the gridelectrode of the gas discharge device a voltage which varies inaccordance with changes in impedance in the attached load cirforexample, be any one of a plurality of different telephone loop circuitshaving widely varying impedances, but the direct current supplied to allof these loop circuits will be substantially the same.

The present application discloses a gas-filled tube which, however, doesnot act as a rectifier of alternating current. The electrodes of thetube are surrounded by an annular electromagnet having its axisconcentric with that of the tube. The electromagnet is supplied withcurrent which is the same as. that supplied to the attached loadcircuit. The magnetic field acts to maintain the current flow throughthe circuit substantially constant and practically independent ofvariations in the impedance of the load circuit.

One of the objects of this invention is, therefore, to obtain asubstantiallyconstant direct current from a gas tube circuit connectedto a source of potential supplying direct current to a load circuit ofvarying impedance. This is accomplished by surrounding the tube with anelectromagnet through the winding of which flows the current to becontrolled. v

This object as well as further features of this invention will be betterunderstood from thedetailed description hereinafter following when readin connection with the accompanying drawing, in which Figure 1represents one embodiment of merely for the purpose of illustration, andFig. 2 illustrates in perspective a portion of the electromagneticallycontrolled gas discharge tube which is an essential part of thisinvention.

Referring to Fig. 1 of the drawin the refer- 'ence character Vdesignates a gas discharge tube comprising a plate or anode P, two gridelectrodes G1 and Ga, a cathode K and a heater H. The heater H issupplied with the necessary heating current by means of a; battery B1.The grid G1 is maintained at a positive potential with respect' to thecathode K by means of a battery 32, the circuit interconnecting the gridG1 with the cathode K including, in addition to the battery B2, a meterM1. The grid electrode G: of the tube V is also maintained at a positivepotential with respect to the cathode K by means of a battery Ba, thegrid electrode G2 being connected to the cathode by a circuit includinga meter M2 in addition to the, battery B3. The anode P of the tube V isconnected to the cathode K by means of a circuit including a coil L, aload circuit or resistor R1, a meter Ma and a battery B4, all arrangedin series relationship. A resistor R2 may, if desired, be comiectedjnshunt with the coil L. l

The coil L is represented schematically in Fig. 1 immediately above thegas tube V, but this coil may be wound in the form of a toroid ordoughnut about the envelope enclosing the electrodes of the tube. Theaxis of the coil will coincide with the vertical axis of the tube. Thecoil L is shown in Fig. 2 positioned about the envelope of the tube V,but cut away in part so as to illustrate that it is located closelyadjacent to the envelope of the tube and about its electrodes, the axisof the coil being coincident with the vertical axis of tube V.

The resistor R1 of Fig. 1 may be any device or circuit having animpedance which may vary I from zero or from some negligible value to avery large value. A telephone loop circuit is one suitable form ofimpedance device, such a circuit or device being shown and described inthe copending application above referred to. The object of the inventionis, in the circuit arrangement of the copending application, to providean apparatus for producing direct current of substantially constantmagnitude which maybe utilized, for example, for supplying telephoneloop circuits with direct current required for telephone purposes, aconstant direct current being essential for efficient telephonecommunication.

The gas discharge tube V may be, for example, of the RK-lOO type, butother gas tube structures having coacting magnetic fields may beemployedin the practice of this invention to obtain a substantially constantdirect current under varying conditions of load. The coil L may becomposed of a plurality of turns of copper wire of smaller diameter, ifdesired, thereby dispensing with the use of any shunt resistor such asR2.

In one installation in which the circuit of Fig. 1 was employed thebatteries 3:, Ba and B4 had terminal voltages of approximately 13, 3 and330 volts, respectively. The coil L, which was positioned coaxiallyabout the envelope of the tube V and in proximity to the enclosedelectrodes, was composed of approximately 13,200 turns of small gaugecopper wire having a resistance approximately 2,524 ohms. The coil L wasabout two inches long, and had an external diameter of 3% inches and aninternal diameter of 2% inches. The'shunting resistor R: was ofapproximately 818 ohms. The current as measured by the meter M1 wasabout 50 miliamperes. The current flowing through the meter M: varied inaccordance with the resistance in the load device R1. As the load deviceR1 was changed from a zero resistance to a value of approximately 1,600ohms, the anode current as measured by the meter 1% varied from between43 to 50 milliamperes. The current flowing in the circuit of the grid(32, as measured by meter M2, varied between 150 and 350 -milliamperes.

The extremely small variation of anode current above noted, with widevariations in the load impedance R1, is of considerable importance intelephone installations where it is desired to obtain a highly constantdirect current. As already stated, the circuit may be connected, forexample, to any one of a plurality of telephone loop circuits ofconsiderably different impedances without introducing any substantialchange in the current flow therethrough.

It will be understood that the tube referred to and the constants of thevarious circuit elementshave been given merely for the purpose ofillustration. They are not to be construed as limitations upon theinvention. It will be understood also that if a larger current isrequired for use in the load circuit device R1 (or in apparatus orcircuits attached thereto), the increased current may be obtained byemploying a coil L of lower resistance and otherwise proportioning it togive optimum efiects.

The maintenance of a substantially constant flow of direct current inthe anode circuit was attested by the observations already referred tohereinabove. The control of the constancy of the current by the locationand geometry or the electromagnet coil L was also determined from thefact that as the coil L was moved further and further away from theenvelope of the tube V, the anode current variations were substantiallywider, and hence lacked the constancy required for telephone uses. Suchcurrents are of practically no utility for the purposes specified.

While this invention has been shown and described in certain particulararrangements merely for the purpose of illustration, it will beunderstood that the general principles of this invention may be appliedto other and widely varied organizations without departing from thespirit oi. the invention and the scope of the appended claims.

What is claimed is:

1. Apparatus for supplying substantially constant direct current to adevice having an impedance which may be varied over a large range,comprising a gas discharge tube including an anode, a cathode and twogrid electrodes, a toroidal electromagnetic coil in close proximity tobut outside the envelope of the tube and having its axis coincident withthe axis of the envelope, said coil impressing a magnetic field upon allor the electrodes of the tube, a source of voltage connected in serieswith the coil and the anode and cathode electrodes of the tube as wellas with said device, and means for applying predetermined positivevoltages to said grid electrodes with respect to said cathode.

2. The combination of a gas discharge tube having a plurality ofelectrodes including an anode, two grid electrodes, and a cathode, asource of potential, a variable impedance device, means for continuouslyapplying predetermined positive potentials to said grid electrodes,means for transmitting substantially constant direct current from saidsource through the anode and cathode path of said tube and through saidimpedance device, said latter means comprisin a toroidal electromagnetthe axis of which coincides with the axis of the tube, saidelectromagnet being positioned in close proximity to but outside theenvelope of the tube, the coil of said electromagnet being connectedbetween said source and said device, the magnetic component of saidelectromagnet being coaxial with the axis of the tube.

JAMES FERGUSON ROUGVIE.

